The 1 5/8's Hedman's will work without dinging anything. I've done so successfully on a 69 with PS and A/C. My guess is, the Dynomax header will work as well because the tubes really hug the block...so much so, that spark plug clearance is an issue. I prefer the Hedmans...one man's opinion. On install, get the front end way off the ground and with the packaging still on the header, install from under the car.
For mufflers, I'd go offset in, offset out. This will keep the two pipes from the headers to the mufflers tucked close to the driveshaft and partiallly in the tunnel. Looks nice too. Offset-out will make it easier for your pipeman to run tailpipes.